This invention relates to a capacitor protective device and more particularly to a protective device and circuit for large power capacitors.
Larger power capacitors were previously filled with a dielectric fluid referred to as a polychlorinated biphenyl. The polychlorinated biphenyls were considered to be essentially non-inflamable. Accordingly, in the unlikely event of a capacitor failure due to perhaps internal arcing and a violent rupture of the capacitor case, the polychlorinated biphenyls would not support combustion and flame problems were minimized. Recently, however, changing conditions have brought about the use of new dielectric liquids in large power capacitors. Many of these new fluids do not have the non-flammability characteristics of the PCB's and therefore support combustion and increase fire hazards in the event of a rupture of a capacitor. A desirable protective device and circuit for a large power capacitor would include an arrangement whereby a visual signal is given to the operating people involved that a capacitor is nearing failure and also an arrangement by which the capacitor is disconnected from the line circuit.
It is therefore an object of this invention to provide a protective device for large power capacitors which functions effectively to disconnect the capacitor from its electrical circuit in event of failure and also provide a visual indication of its failure. More importantly this invention provides a capacitor protective device which senses internal pressure of a capacitor and removes the capacitor from electrical circuit when the pressure increases and prior to its rupture.